Cable construction.



H. W. FISHER.

CABLE CONSTRUCTION. APPLICATION FILED MAB. 24, 1910.

FIGA.

jUNTTED sTATEs PATENT oEEIcE.

HENRY W. FISHER, OF PITTSBURG, PENNSYLVANIA, ASSIGNOR TO STANDARD UNDER-l GROUND CABLE COMPANY, OF PITTSBURG, PENNSYLVANIA, A CORPORATION OFPENNSYLVANIA.

CABLE CONSTRUCTION.

Specification of Letters Patent. Patented J Illy 19, 1910.

Application filed March 24, 1910. Seria-1' No. 551,296.

To all whom it may concern.:

covered certain nevi7 and useful Imorovements in Cable Construction, ofwhich improvements the following 1s a speclticatlion.

My invention relates to means for detectparticular instrumentality whichI employ is the thermal couple, and my invention lies in adaptation ofthe members of the thermal couple itself and in assembling them with thecable strand or strands and inclosingy the whole within the cablesheath.

In the use of electrical cables, the heat generated by the currentflowing in the conc uctor becomes at times so great as to impair ordestroy the cable. 'lhe usual effect of excessive heat is the breakingdown of the insulation, and the consequent escape of current.` Suchaccident is most likely to happen where -the intensity of current isreatest, or where the greatest number o c011- ductors are gatheredwithin a small space conditions which commonly exist in trunk linesleadin from power stations, and like situations. y employing means fordetecting temperature at such a point of strain, and knowing thecritical temperature for the insulation employed, I am able to discoverWeakness in the system and prevent accident of the nature suggestedabove..

My invention consists in adapting the thermal cou le to this particularuse by `forming its e ements of wire, and in gathering the wire or wiresof the thermal couple, properly insulated, with'the conductor orconductors of the cable. In some instances I ind it desirable to employa conductor of the cable as one ofthe elements of the thermal couple. A

In `the accompanyin drawings which form part of this speci cation,Figure 1 is a view in medial longit dinal section of an electricalcablewith m invention applied thereto; and in this figure are also showndiagrammatically an indicator for the thermal couple together with meansfor standardizing the readin Fig. 2 is a view in transverse sectiono thecable of Fig. 1, the plane of section being indicated at II-II,

Fig. 1;' Fig. 3 is a view similar to Fig. l 1llustrat1ng an alternativearrangement which. may be' found preferable under certain circumstances.Fig. 4 is also a View in longitudinal section, illustrating amodification of construction.

Parts Which are repeated in the several gures bear the same referencenumerals in each case. ing temperature Within the body of an elecwiresof di'l'erent metals, 1 and 2, electrically united, as at 3, properlyinsulated from one l another and from the conductor or conduc- Thethermal couple is made up of two tors of the cable, 4, and gatheredwiththe latter Within the cable sheath, 5. The free ends of this couple areelectricall through an indicating device, 6.

united he principle upon which the thermal couple acts is that whenlengths of dissimilar metals are so related to one another, differenceintemperature at opposite ends of the couple effectl a flow of current,which current 1s proportioned in intensity to the inequality intemperature referred to. This being the case, and the union 3 of theelements of the couple being located at the desired point in theinstallation, determination of temperature at that point becomespossible.

In order to standardize the readings ot the instrument 6, and determinenot merely divergence in temperature at opposite ends of the couple, butactual temperature at the remote point, 3, it is only necessary tomaintain the temperature at the accessible end of the couple fixed. Thisis ordinarily accomplished by introducing the free ends of the couple toan ice bath 7.

In order to calibrate the readings of the indicator 6 I may use astandardizing thermal couple of the same metals as employed in thethermal couple of the cable; by varying thetem-perature of theextremities of said standardizing thermal couple the tempera-turescorrespondingto readin s of the indicator canl readily be determine ItWill be understood that the cable length which contains the thermalcouple will ordinarily be assembled in the Shop, and when installed itwill be so placed as to bring the point where theunion 3l is efected tothe desired situation in the system.'

My invention is not limited to the use of any particular metals; thfrange of available material for various ranges of tempera- 'ture is Wellknown to physicists. For very great ranges of temperature, thermalcouple are commonly made of platinum alloys, and are very costly. For mypurposes, involving a, range of not more than 100 degrees C. iron andcopper Will form a serviceable couple, or iron anda metal compound bythe trade-name advance Wire may be employed; though, as Illiave said, Ido not limit myself to any particular metals.

In 4Fig. 3 an arrangement is adopted which is possible Where the couplemay extend throughout the circuit of a cable. The two elements of thecouple instead of being laid side by side within the cable body, lie endto end, in a single Strand, throughout the length of the cable. In thisarrangement also the union 3 will lie at the point in the extent of thecable Where temperature is to be observed.

In liig. 4 one element of the couple, which may be assmned to -be alength pt iron wire properly insulated is the same as in the instancesalready described. The other element in this ease consistsv of a copperWire 2 one of the cable strands.

It will kbe understood that the invention in any one of thesealternative arrangements may be employed in connection with electricalcables of various constructions, whether single-conductor ormultiple-conductor milles, or whether the cable be formed my hand.

in lead or.

lie side by side, as in Fig. 1, it will be understood that the point ofunion 3 need not be at the extremity of the parallel lines, but

may lie at some intermediate point.; in which ease all of one strand anda portion of the other wlll be of one metal and the' remainder of thesecond strand will beA of the othel metal.`

l. claim herein as my invention:

1. In an electrical cable the combination with the cable conductor of athermal couple whose members are assembled with the cable conductor inthe make-up of the cable, substantially as described.

2. In a cable structure the combination with a cable strand and a strandof a dis-` similar metal, thel cable' strand and the strand ofdissimilar metal being electricall)r connected at the opposite ends ofthe latter, to form a thermal couple, substantially as described.

n testimony whereof, I have hereunto set HENRY W. msnen. lVitnesses:

Amen A. TRIM.,

lla/matas J. ToiuAssoN.

